There are many known methods for delivering medicine to animals. One of the most common and well known methods is the syringe, used for injecting medicine under the skin or into the musculature of an animal. Handheld syringes may be used to deliver medicine; however, they require close proximity to the animal, which is often not desirable. Many methods have been developed for injecting animals from a safe distance via projection of the injecting apparatus, most commonly, a syringe. The more successful of these projectile syringes result in accurate placement of the syringe, quick injection of the medicament upon contact with the animal, safe handling of the syringe prior to projection and after injection into the animal, proper pressurization of the syringe during flight, and minimal tissue damage to the animal.
Several variations of projectile syringes have been put forth, a majority of which involve a plunger piston that must be depressed by force and either do not include a tailpiece or include only simple guide fins. U.S. Pat. No. 3,715,990 discloses a dart projectile with a cylinder plunger piston that encompasses an explosive charge. The impact of the projector causes an explosive charge, which depresses the plunger piston causing the medication to be injected into the animal. U.S. Pat. No. 6,482,187 discloses a syringe including a barrel, a plunger piston which moves longitudinally within the barrel in response to air pressure within the barrel, and a syringe needle for penetrating the hide of an animal and for introducing medication to the animal. Prior to loading the syringe into the projector, the medication chamber is filled with medicine and the syringe is then pressurized. As is common when a plunger piston is used, the syringe has no tailpiece to speak of, consisting of the plunger piece instead. U.S. Pat. No. 4,102,893 proposed a syringe with an alternative to the plunger piston projectile utilizing the force impact with the animal to release a piston by means of a triggering pin. However, such mechanical force impact syringes are unreliable when used with a CO2(g) fired projector or an air gun and are generally limited to use with a blowgun or similar device.
A more desirable syringe would instead utilize a one-way valve mechanism, enabling the syringe to be pressurized either by hand prior to being fired from the projector or by the action of the projector in firing the syringe. Such a valve mechanism would eliminate the need for a plunger piston, explosive charge and/or a mechanical force of impact triggering mechanism and allows for the use of a greater variety of projectors including compressed gas projectors such as a CO2(g) fired projectors and air guns. Additionally, the desired syringe would include a tailpiece that would allow air to flow through and around the fins thereby increasing stability in flight and allowing for greater accuracy of syringe dart placement over a greater trajectory and in inclement weather and windy conditions. The desired syringe would also include a safety cap that would be punctured by the needle only upon impact with the animal's hide and would then slide back into a hub on the syringe. The desired syringe with such a safety cap would then be safe for storage and loading into the projector without harm to humans.